Global energy security and climate change put forward the requirements for energy conservation and emissions reduction upon on the existing automobile technology. Therefore the multinational efforts have been made on research and development of automobile model transformation and technological innovation, especially focused on the development of new energy and clean energy, recovery and utilization of braking energy, hybrid power, etc.
In recent years, a number of news release and demo achievements have presented a type of compressed-air cars, such as MDI (Motor Development International) in France, Tata Motors in India, etc. They use a kind of compressed air engine to drive vehicles, wherein the air is compressed by an electric air compressor into the vehicle-mounted compressed air tank as power source, referred to as existing technology compressed-air vehicles.
For the above existing technology compressed-air vehicles, the compressed air from the vehicle-mounted compressed air tank is heated and injected into the vehicle-mounted compressed air engine, pushing the pistons to drive the crankshaft rotating, and the vehicle running, which mileage and speed need to improve, upon the improvement and full utilization of the vehicular compressed air energy storage. The existing technology compressed-air vehicles are generally equipped with a second propulsion system, focusing on braking energy recycling and/or as an auxiliary power, that is, using vehicular compressed air engine and electric motor or internal combustion engine as hybrid power, wherein the mileage powered by electric motor or combustion engine accounts for a large proportion of the travel of the existing technology compressed-air vehicles. While electric motor or internal combustion engine used in such hybrid power have their respective problems: such as electric power portion comprises larger battery, motor and generator (or motor-generator), significantly increasing the vehicle weight, in contradiction to “lightweight”, one of development trends of compressed air vehicles; the more serious problem is the environmental pollution of battery, polluting the soil, more difficult to deal with than polluting air or water resources; one can imagine the disaster to future generations after thousands, hundreds of millions of large batch after batch of batteries would be abandoned. As for the internal combustion engine power, it has been known that the standard internal combustion engines have only about 30% of the efficiency even under very good conditions, meaning that “70% of energy in each gallon of gasoline leave cars as waste heat”, inconsistent with the purpose to develop compressed-air vehicles as future economic and environmentally friendly vehicles. In 2012, this inventor made an authorized patent “Automobile brake energy storing-releasing driving device” (patent No. ZL 2012 2 05111952), the PCT International application “Device for vehicle energy storage/release when braking/actuating and method thereof” (International application No. PCT/SE2013/000100), which can store the kinetic energy, lost during automobile deceleration and braking in the form of air pressure potential energy, and release it in the form of kinetic energy during automobile starting and acceleration. This recent automobile brake energy recycling device has not been widely used yet.
Furthermore, whether or not any kind of new energy vehicles is capable for energy saving and emission reduction should be considered upon the energy consumption and emission not only during vehicle's running, but also during the process producing and supplying the new energy.
The existing technology compressed-air vehicle uses electric air compressor to pressurize and inflate the compressed air as an energy source into the vehicle-mounted compressed air tank, wherein some capable families can try to use household electric air compressor to pressurize and inflate the compressed air into the vehicle-mounted compressed air tank while most of the users use larger power air compressors at service stations. Physical experiments have shown that a gas is rapidly compressed with increasing its temperature, while quickly expanding with decreasing its temperature. According to the authorized determination, only 10% of electrical energy consumed by electric air compressor can be transmitted into the compressed air, while the remaining 90% is converted into heat energy. So much of heat energy is not needed for any of existing technology compressed air vehicles but a large amount of waste heat produced during the process of pressurizing and inflating air into the vehicle-mounted compressed air tank. It has been reported that, without a cooling step, a high temperature of 1000° C. can be reached when compressing air. The above process of pressurizing and inflating air into the vehicle-mounted compressed air tank is provided with inter-cooling, including a “four-stage air compression with inter-cooling”, that is, the air compression proceeds in 4 stages where the air with a temperature increased after the first stage compression is cooled before the second stage compression . . . up to 4 stages, between which there are 3 steps of inter-cooling accompanied by a remarkable loss of thermal energy. When using electric air compressor to pressurize and inflate air respectively into one compressed air tank after another mounted on the corresponding existing technology compressed-air vehicles, it is not so easy to make centralized recovery and effective use of those batches of waste heat produced during the process. As a result, the air temperature in the vehicle-mounted compressed air tank is also increased and this part of heat energy is consumed onboard if the compressed air in the tank is not fully cooled when the pressurizing and inflating process ends. Then during the air temperature in the tank drops the air pressure in the tank is to drop as its temperature does, resulting in the automatic decrease of energy storage in the vehicle-mounted compressed air tank, therefore a rapid and effective cooling facility onboard is correspondingly needed in order to retard the severity of this happening. The comprehensive and cumulative calculations have indicated a great loss of electric energy in such an approach to produce and supply the compressed air, significantly reducing the superiority of the existing technology compressed-air vehicles in energy-saving and emission reduction.